Games Domain has a couple screenshots from Quake IV posted that are worth checking out. Quake IV is an all new story that will pick up right where Quake II left off. Here is a clip from what our friends at Raven had to say to Games Domain:

"After destroying the Strogg's collective brain and leader -- the Makron -- the Strogg have quickly regrouped under a new and more powerful Makron. However, with the Strogg's planetary defenses still destroyed, Earth's forces can deliver a full and final assault. This time you're not alone. An army of soldiers are fighting with you and an arsenal of weapons and vehicles are at your disposal. Quake IV delivers you deeper into the heart of Stroggos."